1 Students mustn't eat in the lecture halls:it's not allowed.
2 It's raining out. You should take an umbrella.
3 Why didn't she tell us about her problems? We could help her.
4 Nick didn't need (didn't have to) to take the bus because his cousin offered to give him a lift.
5 Soldiers must obey without question.
6 He must be working in library now. I've just seen him.
7 You needn't have come here to tell me. You could call me instead.
8 I had no key, I had to wake my mother and she let me in.
9 I'm so tired, I really should/need to go to bed now.
10 Despite playing under strength, the team could beat their riveals.